Purpose: To create an elevation model in support of the Yakima River Basin Water Storage Feasability Study (YRBWSFS) hydraulic modeling effort. The hydraulic modeling was conducted to help determine fish habitats at different flow levels.

Access_Constraints:
The USDI Bureau of Reclamation (Reclamation) provides public domain spatial data without restrictions. Access to spatial data that are considered 1) works in-progress, 2) for internal use, or 3) confidential, sensitive, or private may be restricted. Access to such data may require a Freedom of Information Act (FOIA) request. For further information, contact the Geospatial Data Administrator (see Point of Contact info).

Use_Constraints:
The USDI Bureau of Reclamation (Reclamation) provides spatial data """"""""as-is"""""""" without warranty of any kind, expressed or implied, including but not limited to, any warranties of fitness for a particular purpose. The burden for determining fitness for use lies entirely with the user. In no event will the producers of Reclamation spatial data be liable for any damages arising from the use of, or the inability to use, these data. The user assumes all responsibility for spatial and attribute accuracy, completeness, validity, and appropriateness with regard to the suitability of these spatial data for any specific use or application, and such use or application is at the user's own risk.

Data_Quality_Information:
Attribute_Accuracy:
Attribute_Accuracy_Report:
The only attributes refer to the z coordinates or reach locations. The attribute accuracies for the z coordinates are directly tied to the accuracy of the data set. These attributes were cross checked by TSC; Reclamation employees for correctness. The reach locations were added by UCAO; Reclamation employees and double checked.

Logical_Consistency_Report:
All data collection was conducted by the same source (Fugro Pelagos,Inc). The finished data was cross checked by TSC; Bureau of Reclamation staff for correctness. As part of the process, data was compared against field surveys conducted at the same time as the data collection flight. For further information, see the 'Process' description.

Completeness_Report:
Data set was created to cover portions of the Yakima and Naches River. The areas designated were completely covered.

Positional_Accuracy:
Horizontal_Positional_Accuracy:

Horizontal_Positional_Accuracy_Report:
The horizontal accuracy value is based on the published accuracies for the equipment used. However, it is believed that the accuracy values are greater than those listed.

Quantitative_Horizontal_Positional_Accuracy_Assessment:
Horizontal_Positional_Accuracy_Value: 0.25
Horizontal_Positional_Accuracy_Explanation: Published accuracies for the SHOALS-1000T equipment.

Vertical_Positional_Accuracy:
Vertical_Positional_Accuracy_Report:
The vertical accuracy value is based on the published accuracies for the equipment used. However, it is believed that the accuracy values are greater than those listed.
The following is a summary of the accuracies found by comparing the raw data to surveyed locations. Median values of the residuals from the statistical analysis range from 0.492 feet (0.15 m) to 0.853 feet (0.26 m).

This data has been corrected to take into account the amount equal to the median value of the residuals of each reach obtained by subtracting the LiDAR elevations from the ground truth elevations. For more information, see the process section.
The elevational accuracy value could therefore be closer to 0.1.

Quantitative_Vertical_Positional_Accuracy_Assessment:

Vertical_Positional_Accuracy_Value: 0.25
Vertical_Positional_Accuracy_Explanation: Published accuracies for the SHOALS-1000T equipment.

This bathymetry was collected and processed by Fugro Pelagos,Inc. using a SHOALS-1000T LASER (manufactured by Optech, Inc.) sensor capable of penetrating water using a blue-green LASER. Terrestrial measurements are also possible with this unit although none was acquired with this bathymetry. The data was processed with Optech software using what is being called the "Inland Water Algorithm". This algorithm was developed to process those returns from depths from less than approximately 4.9 feet (1.5 meters). The "Inland Water Algorithm" processes data acquired from depths to approximately 13 feet (4 m). The Sept. 2004 data was the first application of this algorithm and use of the SHOALS-1000T in shallow water riverine environments.

The published specification and accuracies for the SHOALS-100T are as follows: The SHOALS-1000T is capable of recording x-y-z data at a rate of 1000 Hz with a sounding density of 6.6x6.6, 9.8x9.8, 13.1x13.1 and 16.4x16.4 feet (2x2, 3x3, 4x4 or 5x5 m). The point data for the bathymetry meets Order 1 accuracy standards of the International Hydrographic Organization (IHO) with a horizontal accuracy of 8.2 feet (2.5 m) and a vertical accuracy of 0.8 feet (0.25 m, 1 sigma). For more information regarding instrument specifications visit http://www.optech.on.ca. This site also contains information on the history of the development of the SHOALS unit. For more information on hydrographic surveying accuracies and the IHO refer to chapter two of the U.S. Army Corps of Engineers Hydrographic Survey manual at http://www.usace.army.mil/inet/usace-docs/eng-manuals/em1110-2-1003/toc.htm.

It is likely that water clarity is the single most limiting factor for collecting bathymetric data with LiDAR. The minimum required clarity is measured with a Secchi disc and is called the Secchi depth. A Secchi disc is available in various weights and diameters (approximately 8 - 20 inches, 20 - 50 cm) with the circle typically divided into four evenly divided pie-shaped wedges in alternating black and white. The Secchi depth is determined by lowering the disc into the water column and recording the depth at which the black and white portions of the disc can no longer be distinguished. The minimum visibility requirement for successful LiDAR penetration using the SHOALS-1000T is 2.5 times the Secchi depth up to a depth of 164 ft (50 m) (www.optech.on.ca).

The LASER is not capable of penetrating the water column where bubbles are present, such as white water conditions. The LASER is also incapable of penetrating vegetation, whether that vegetation is growing under the water surface or overhanging above the surface. These limitations are very similar to the limitations of SONAR when operated from a boat. Bubbles foul acoustic signals to the same extent as optic signals. Overhanging vegetation or tall vegetation near the channel banks often prohibits the reception of a sufficient number of satellites or signal from the base station when performing a SONAR survey with RTK GPS surveying equipment.

Ground truth data was collected with RTK GPS at a minimum of one location per reach flown. For the Lower Kittitas data set, there was additional survey data to use for comparison that was collected in August 2003 by SONAR and RTK GPS surveying equipment mounted on a raft. Using these data, a statistical analysis was performed for each data set to determine precision and accuracy. From these analyses conclusions were made regarding the bias and recommended adjustments to the data.

It was determined that the best method for adjusting the elevations provided by the LiDAR is to correct by an amount equal to the median value of the residuals obtained by subtracting the LiDAR elevations from the ground truth elevations. Reasons for the bias are currently unknown and will be investigated by personnel at Reclamation, Fugro Pelagos and Optech. The advertised precision of the LiDAR is +/- 0.83 feet (0.25 m). Standard deviations from the statistical analysis range from 0.492 feet (0.15 m) to 0.853 feet (0.26 m).

Resource_Description: Downloadable Data
Distribution_Liability:
The USDI Bureau of Reclamation (Reclamation) provides spatial data ""as-is"" without warranty of any kind, expressed or implied, including but not limited to, any warranties of fitness for a particular purpose. The burden for determining fitness for use lies entirely with the user. In no event will the producers of Reclamation spatial data be liable for any damages arising from the use of, or the inability to use, these data. Reclamation liability is limited to providing a replacement copy for requested data sets that are not readable upon receipt.

The user assumes all responsibility for spatial and attribute accuracy, completeness, validity and appropriateness with regard to the suitability of these spatial data for any specific use or application, and such use or application is at the user's own risk.

Spatial data provided by the Reclamation are public domain, and the recipient may not assert any proprietary rights thereto nor represent data sets as other than government-produced data.